to be open to something = to be willing to try something So this blogger is saying that they are willing to try being in a relationship (and we all assume the blogger is not currently in a relationship!). Often, but not always, by using this language, the speaker is indicating that the "something" might be a bit uncomfortable or anxious for them. "I am open to sushi." means "I am willing to try sushi." "I am open to going to your mother's house." means "I am willing to go to your mother's house."

It means you have shown your frankly attitude towards your lover, But do not have any cheat or hide for that. So that you can start a faithful relationship with the others.

そのブロガーが「彼氏/彼女募集中」だということですよ。

Thank you for your comment. I got it. The blogger was just a stranger for me. I only happened to read the person's blog.

Yes, you are right. That means we should not too conservative and had better show our loves with our openmind. Am I right?